Pseudo wire label reflector, an edge equipment, and a two-layer virtual network

ABSTRACT

A pseudo wire label reflector, based on a existing label distribution router, further includes: a mode management unit, for determining the mode for switching and transferring a pseudo wire label message; a first session management unit, for saving the support information that LDP signaling session connection supports the pseudo wire label reflecting capacity; a first pseudo wire label receiving unit, for receiving a pseudo wire label message; a first pseudo wire management unit, for saving the switched pseudo wire state and deciding whether to modify the pseudo wire label message according to the switch and transfer mode determined by the mode management unit; a first pseudo wire label sending unit, for sending the pseudo wire label message. The invention also provides an edge apparatus and a L2 VPN. The present invention makes PE equipments participating pseudo wire service to set up PSN tunnel and LDP signaling session connection with the pseudo wire label reflector by introducing the pseudo wire label reflector and extending the capacity that the current edge apparatus supports the pseudo wire label reflector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/632,445, filed Dec. 21, 2007, entitled “A Pseudo Wire LabelReflector, an Edge Equipment, a Two-Layer Virtual Network and a Methodof Providing Pseudo Wire Service,” the entirety of which is herebyincorporated by reference, which was the National Stage of InternationalApplication No. PCT/CN2005/000001, filed Jan. 4, 2005, the entirety ofwhich is also hereby incorporated by reference, which claims priority toChinese Patent Application No. 200410062494.2, filed Jul. 12, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the technique of virtual private network,especially to the technique of L2 virtual private network (L2 VPN).

2. Background of the Invention

In the data communication network, packing and transporting L2 protocoldata units (L2 PDU) by pseudo wire (PW) could provide emulation L2service through IP/MPLS (Multiprotocol Label Switching) backbonenetwork. The network adopting this technology can be referred to as a L2virtual private network (L2 VPN). At present, there are two types of theL2 VPN based on providers:

One is the network providing virtual private wire service (VPWS). In theVPWS frame protocol (as further described in, PWE3 Architecture,draft-ietf-pwe3-arch-04.txt), the network model providing pseudo wireemulation edge-to-edge (PWE3) service is given. In the VPWS signalingprotocol (as set forth in, Pseudo Wire Setup and Maintenance using LDP,draft-ietf-pwe3-control-protocol-06.txt), a label distribution protocol(LDP) signaling mechanism establishing and maintaining pseudo wiresbetween the edge equipments of the backbone network (commonly referredto as provider edge, PE) is given.

The other is the network providing virtual private LAN service (VPLS),which raises a L2 address-based switching function on the basis ofestablishing pseudo wire between PE equipments. In the network, theestablishment and maintenance of the pseudo wire could adopt two typesof signaling mechanisms which are LDP and multiprotocol-extension bordergateway protocol (MP-BGP), but the LDP signaling mechanism is commonlyadopted, as can refer to Virtual Private LAN Services over MPLS,draft-ietf-l2vpn-vpls-ldp-03.txt.

In above-described two types of L2 VPN, the network model whichestablishes and maintains the pseudo wire by utilizing LDP is flat. Itis necessary to establish an edge-to-edge backbone network tunnel (alsoreferred to as packet switching network tunnel or PSN tunnel) and adirect LDP signaling session connection between PE equipments providingpseudo wires. When the network becomes very big and the pseudo wireservice on the backbone network increases explosively, this full meshtunnel and signaling connection will lead to the problem in networkscalability. Additionally, when need to provide cross-domain pseudo wireservice, it will be even the problem to be solved how to establish lotsof cross-domain PSN tunnels and LDP session connections.

BRIEF SUMMARY OF THE INVENTION

The invention is provided in view of the above problems in the priorart. The object of the invention is to provide a pseudo wire labelreflector which can support pseudo wire label reflection.

Another object of the invention is to provide an edge equipment whichcan support the label distribution reflector.

Another object of the invention is to provide a L2 virtual privatenetwork which can solve problems in scalability of a L2 VPN in the priorart.

According to the first aspect of the invention, a pseudo wire labelreflector is provided, comprising: a signaling receiving/sending unitfor receiving and sending a label distribution protocol (LDP) signalingmessage; a pseudo wire label list for saving a pseudo wire label and therelated information; a packing/unpacking unit for packing a L2 datapackage into a multiprotocol label switching data package and unpackinga multiprotocol label switching data package into a L2 data package; amultiprotocol label switching and forwarding unit for receiving andsending a multiprotocol label switching data package; a mode managementunit for determining the mode of switching and forwarding a pseudo wirelabel message; a first session management unit for storing the supportinformation that the label distribution protocol signaling sessionconnection supports pseudo wire label reflecting capacity; a firstpseudo wire label receiving unit for receiving a pseudo wire labelmessage; a first pseudo wire management unit for storing the switchedpseudo wire state, and determining whether to modify the pseudo wirelabel message according to the switch and transfer mode determined bythe mode management unit; and a first pseudo wire label sending unit forsending a pseudo wire label message.

Preferably, the pseudo wire label reflector further comprises: a firstcapacity negotiation unit for exchanging the information supporting thepseudo wire label reflect capacity with neighbors.

Preferably, the pseudo wire label reflector further comprises: a secondpseudo wire management unit for storing the pseudo wire state when thepseudo wire label reflector is used as an edge equipment.

Preferably, the first and second pseudo wire management unit furthercomprise: a device for comparing the priorities of the pseudo wire labelmessages, a device for choosing the pseudo wire label, and a device forwriting the pseudo wire labels into the pseudo wire label list.

Preferably, the device for choosing the pseudo wire label chooses thepseudo wire label whose priority is the highest as the pseudo wirelabel.

Preferably, the device for choosing a pseudo wire label adopts a loadbalance strategy to choose the pseudo wire label.

Preferably, the pseudo wire label reflector further comprises: aneighbor capacity configuration unit for designating that the neighborshave the capacity negotiation function.

According to the second aspect of the invention, an edge equipment isprovided, comprising: a signaling receiving/sending unit for receivingand sending a label distribution protocol signaling message; a pseudowire label list for depositing pseudo wire labels and the relatedinformation; a packing/unpacking unit for packing a L2 data package intoa multiprotocol label switching data package and unpacking amultiprotocol label switching data package into a L2 data package; amultiprotocol label switching and transferring unit for receiving andsending the multiprotocol label switching data package; a second sessionmanagement unit for storing the information about the neighbors who arepseudo wire label reflectors; a second pseudo wire label receiving unitfor receiving a pseudo wire label message; a third pseudo wiremanagement unit for storing the pseudo wire state; and a second pseudowire label sending unit for sending the pseudo wire label message.

Preferably, the edge equipment further comprises: a second capacitynegotiation unit for switching the information supporting the pseudowire label reflect capacity with neighbors.

Preferably, the third pseudo wire management unit further comprises: adevice for comparing the priorities of the pseudo wire label messages, adevice for choosing the pseudo wire label, and a device for writing thepseudo wire label into the pseudo wire label list.

Preferably, the device for choosing the pseudo wire label chooses thepseudo wire label whose priority is the highest as the pseudo wirelabel.

Preferably, the device for choosing the pseudo wire label adopts a loadbalance strategy to choose the pseudo wire label.

According to the third aspect of the invention, a L2 virtual privatenetwork is provided, comprising: at least one above-described pseudowire label reflectors and at least two above-described edge equipments,wherein at least two of the at least two edge equipments adopt a labeldistribution protocol to establish signaling session connection by theat least one pseudo wire label reflector.

Comparing with the prior art, the invention introduces the pseudo wirelabel reflector into the L2 virtual private network (L2 VPN) and extendsthe capacity of the existing edge equipment (PE) supporting the pseudowire label reflector so that the PE equipments participating in thepseudo wire service could establish a star or semi-mesh packet switchingnetwork (PSN) tunnel and a label distribution protocol (LDP) signalingsession connection with the pseudo wire label reflector respectively.The occurrence of the full mesh PSN tunnel and LDP signaling sessionconnection are avoided by the pseudo wire label reflector switching thepseudo wire label message and the data flow on the pseudo wire.Therefore, the scalability of the network is enhanced which benefits theoperation and management of the network. Additionally, the pseudo wireservice can also be provided by the pseudo wire label reflector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the pseudo wire label reflector accordingto one embodiment of the invention;

FIG. 2 is a block diagram of the edge equipment according to oneembodiment of the invention;

FIG. 3 is a flow chart of providing pseudo wire service according to oneembodiment of the invention;

FIG. 4 is a schematic diagram of providing pseudo wire service in the L2virtual private network of one embodiment of the invention according toanother embodiment of the invention, wherein the pseudo wire labelreflector adopts simple switch and transfer mode;

FIG. 5 is a schematic diagram of providing pseudo wire service in the L2virtual private network of yet another embodiment of the inventionaccording to yet another embodiment of the invention, wherein the pseudowire label reflector adopts “next hop self” transfer mode;

FIG. 6 is a schematic diagram of providing pseudo wire service in the L2virtual private network including multiple pseudo wire label reflectorsof yet another embodiment of the invention according to yet anotherembodiment of the invention;

FIG. 7 is a schematic diagram of providing cross-domain pseudo wireservice according to yet another embodiment of the invention, wherein anautonomous domain border router (ASBR) is used as a pseudo wire labelreflector;

FIG. 8 is a schematic diagram of providing cross-domain pseudo wireservice according to yet another embodiment of the invention, wherein anautonomous domain border router (ASBR) is not used as a pseudo wirelabel reflector.

DETAILED DESCRIPTION OF THE INVENTION

It is believed that the above and other objects, characteristics andadvantages of the invention will be understood more clearly bydescribing the preferred embodiments of the invention in conjunctionwith the figures below.

In a L2 virtual private network, a bidirectional pseudo wire is composedof two unidirectional label switching paths (LSP). In the detaileddescription below, for simplicity (and not lose generality), the pseudowire is discussed by using the LSP in one data flow direction. Theingress label switching router (LSR) in this data flow direction isreferred to as an ingress edge equipment (PE) or upstream PE, whereasegress LSR is referred to as an egress PE or downstream PE. The pseudowire label message is distributed from downstream PE to upstream PE,whose direction is opposite to the direction of LSP. Therefore, as forthe pseudo wire label message, the downstream PE is referred to as asource PE, the upstream PE is referred to as a target PE.

FIG. 1 is a block diagram of the pseudo wire label reflector 10according to one embodiment of the invention. As shown in FIG. 1, thepseudo wire label reflector 10 includes: a signaling receiving/sendingunit 101 for distributing a protocol (LDP) signaling message byreceiving and sending a label, and for establishing signaling sessionconnections with other pseudo wire label reflectors or edge equipments;a pseudo wire label list 102 for depositing a pseudo wire label and therelated information, and is provided for using by a packing/unpackingunit 103 and the multiprotocol label switching and transferring unit 104as described below; the packing/unpacking unit 103 for packing a L2 datapackage into a multiprotocol label switching (MPLS) data package byadopting the pseudo wire label provided in the pseudo wire label list102 upon receiving the L2 data package and unpacking the received MPLSdata package into a L2 data package; the multiprotocol label switching(MPLS) and transferring unit 104 for receiving and sending a MPLS datapackage according to the related information provided in the pseudo wirelabel list 102. The above-described units are substantially the same asthe units in the existing label distribution router (LDP).

Additionally, the pseudo wire label reflector 10 further includes: amode management unit 110 for determining the switch and transfer modewhich the present pseudo wire label reflector 10 adopts to transfer thereceived pseudo wire label message, and for outputting it into a firstpseudo wire management unit 113 described below; a first sessionmanagement unit 111 for storing and maintaining the support informationthat the LDP signaling session connection supports pseudo wire labelreflecting capacity, which is used as the control information of a firstpseudo wire label sending unit 114 described below; a first pseudo wirelabel receiving unit 112 for receiving the pseudo wire label message bythe signaling receiving/sending unit 101 and outputting it to a firstpseudo wire management unit 113 described below; the first pseudo wiremanagement unit 113 for storing the pseudo wire state switched andtransferred by the present pseudo wire label reflector 10, andoutputting the related information to the pseudo wire label list 102,while determining whether to modify the pseudo wire label messageaccording to the switch and transfer mode determined by the modemanagement unit 110; the first pseudo wire label sending unit 114 forreceiving the pseudo wire label message from the first pseudo wiremanagement unit 113 and sending it by the signaling receiving/sendingunit 101.

Preferably, the mode of switching and transferring the pseudo wire labelmessage includes both simple switch and transfer and “next hop self”transfer. If the mode is simple switch and transfer, transfer theinformation in the pseudo wire label message without modification; ifthe mode is “next hop self” transfer, modify the information in thepseudo wire label message and modify the next hop identifier transferredby the data on the pseudo wire into itself.

It can be known from the above description, by adopting the presentembodiment, the pseudo wire label message can be transferred to otherpseudo wire label reflectors and edge equipments. During transferringthe pseudo wire label message, it can be designated as the next hoptransferred by the data on the pseudo wire (that is, LSP next hop)according to the transfer mode. As well, other pseudo wire labelreflectors used as the LSP next hop are supported.

Furthermore, the pseudo wire label reflector 10 further includes: afirst capacity negotiation unit 115 for exchanging the informationsupporting the pseudo wire label reflect capacity with neighbors (edgeequipments or other pseudo wire label reflectors) by the signalingreceiving/sending unit 101 and outputting it into the first sessionmanagement unit 111, wherein the information comprising whether theysupport pseudo wire label reflection and whether they are pseudo wirelabel reflector neighbors.

It can be known from the above description, by adopting the presentembodiment, the supporting capacity that the neighbors support thepseudo wire label reflection and the reflector neighbors can be furtheridentified.

Furthermore, the pseudo wire label reflector 10 further includes: asecond pseudo wire management unit 116 for storing the pseudo wire statewhen the present pseudo wire label reflector 10 is used as an edgeequipment (PE) and for outputting the related information into thepseudo wire label list 102, while sending the pseudo wire label messageto the first pseudo wire label sending unit 114. If it is indicated inthe pseudo wire label message received by the first pseudo wire labelreceiving unit 112 that the target PE of the pseudo wire label is thepresent pseudo wire label reflector, the second pseudo wire managementunit 116 saves the pseudo wire state and outputs the related informationinto the pseudo wire label list 102; when the pseudo wire labelreflector 10 is configured with a pseudo wire of a local egress (virtualcircuit), the second pseudo wire management unit 116 sends the pseudowire label message generated locally to the first pseudo wire labelsending unit 114.

It can be known from the above description, by adopting the presentembodiment, the pseudo wire label reflector can be used as an edgeequipment.

When the pseudo wire label reflector 10 receives multiple pseudo wirelabel messages of one pseudo wire, the first pseudo wire management unit113 and the second pseudo wire management unit 116 need to choose apseudo wire label. Therefore, the first pseudo wire management unit 113and the second pseudo wire management unit 116 further include: a devicefor comparing the priorities of the pseudo wire label messages, a devicefor choosing a pseudo wire label, and a device for writing the pseudowire label into the pseudo wire label list 102, wherein the device forchoosing the pseudo wire label chooses the pseudo wire label whosepriority is the highest as the pseudo wire label. Optionally, the firstpseudo wire management unit 113 and the second pseudo wire managementunit 116 could adopt the load balance strategy to choose the pseudo wirelabel so that the flux on the pseudo wire are load shared on multiplelabel.

It can be known from the above description, by adopting the presentembodiment, the priority of the pseudo wire label could be supported.

Furthermore, the pseudo wire label reflector further includes a neighborcapacity configuration unit. When the neighbors can not support thecapacity negotiation function, the pseudo wire label reflector candesignate the capacity negotiation function of the neighbors inconfiguration manner.

FIG. 2 is a block diagram of the edge equipment 20 according to oneembodiment of the invention. As shown in FIG. 2, the edge equipment 20includes: a signaling receiving/sending unit 201 for establishing LDPsignaling session connections with other pseudo wire label reflectors oredge equipments by receiving and sending a LDP signaling message; apseudo wire label list 202 for depositing pseudo wire labels and therelated information, and is provided for using by a packing/unpackingunit 203 and a multiprotocol label switching and transferring unit 204described below; the packing/unpacking unit 203 for packing a L2 datapackage into a MPLS data package upon receiving the L2 data package byadopting the pseudo wire label provided in the pseudo wire label list202 and unpacking the received MPLS data package into a L2 data package;the multiprotocol label switching and transferring unit 204 forreceiving and sending the MPLS data package according to the relatedinformation provided in the pseudo wire label list 202. Theabove-described units are substantially the same as the units in theexisting edge equipment (PE).

Furthermore, the edge equipment 20 further includes: a second sessionmanagement unit 210 for storing the information about which neighborsare the pseudo wire label reflectors; a second pseudo wire labelreceiving unit 211 for outputting the pseudo wire label message to athird pseudo wire management unit 212 described below for processingwhen receiving the pseudo wire label message by the signalingreceiving/sending unit 201; the third pseudo wire management unit 212for storing the pseudo wire state and sending the related information tothe pseudo wire label list 202, while sending the pseudo wire labelmessage to a second pseudo wire label sending unit 213; the secondpseudo wire label sending unit 213 for sending the pseudo wire labelmessage sent by the third pseudo wire management unit 212 via thesignaling receiving/sending unit 201 upon receiving it. If it isindicated in the pseudo wire label message received by the second pseudowire label receiving unit 211 that the target PE of the pseudo wirelabel is the present edge equipment, the third pseudo wire managementunit 212 saves the pseudo wire state and outputs the related informationto the pseudo wire label list 202; then sends the pseudo wire labelmessage generated locally to the second pseudo wire label sending unit213.

It can be known from the above description, by adopting the presentembodiment, the pseudo wire label reflector could be supported toreceive the pseudo wire label message from the pseudo wire labelreflector neighbors.

Furthermore, the edge equipment 20 further includes: a second capacitynegotiation unit 214 for exchanging the information supporting thepseudo wire label reflect capacity with neighbors (edge equipments orother pseudo wire label reflectors) by the signaling receiving/sendingunit 201 and outputting it into the second session management unit 210,wherein the information comprising whether supports the pseudo wirelabel reflection and whether they are pseudo wire label reflectorneighbors.

It can be known from the above description, by adopting the presentembodiment, the reflector neighbors can be further identified.

When the edge equipment 20 receives multiple pseudo wire label messagesof one pseudo wire, the third pseudo wire management unit needs tochoose a pseudo wire label. Therefore, the third pseudo wire managementunit 212 further includes: a device for comparing the priorities of thepseudo wire label messages, a device for choosing the pseudo wire label,and a device for writing the pseudo wire label into the pseudo wirelabel list 202, wherein the device for choosing a pseudo wire labelchooses the pseudo wire label whose priority is the highest as thepseudo wire label. Optionally, the third pseudo wire management unit 212could adopt the load balance strategy to choose the pseudo wire label sothat the flux on the pseudo wire are load shared on multiple labels.

It can be known from the above description, by adopting the presentembodiment, the priority of the pseudo wire label could be supported.

Furthermore, the invention provides a L2 virtual private networkincluding at least one above-described pseudo wire label reflector andat least two above edge equipments, wherein at least two edge equipmentsadopt LDP protocol to establish signaling session connection by onepseudo wire label reflector. By adopting the present network, since thepseudo wire label reflector is added, the double end PEs participatingin the pseudo wire service could establish a star or semi-mesh PSNtunnel and a LDP signaling session connection with the pseudo wire labelreflector respectively. Therefore, the occurrence of the full-mesh PSNtunnel and the LDP signaling session connection are avoided so that thevirtual private network have better network scalability.

FIG. 3 is a flow schematic diagram of providing pseudo wire serviceaccording to an embodiment of the invention. In step 301, a pseudo wirelabel reflector and an edge equipment (PE) determine whether neighborssupport pseudo wire label reflection and whether they are the pseudowire label reflector neighbors by negotiation. In step 305, a source PEsends a pseudo wire label message to all the pseudo wire label reflectorneighbors who establish signaling session connection thereto. In thepresent embodiment, by extending the information related to the doubleend PEs of the pseudo wire in the pseudo wire label message, the targetPE (that is, the target that the pseudo wire label transferred to) inthe pseudo wire label message could be identified by the pseudo wirelabel reflector. The extending to the pseudo wire label message will bedescribed in detail hereinafter. If the signaling session connection isestablished directly between the source PE and the target PE, the sourcePE will also send the pseudo wire label message to the target PE. Instep 310, upon receiving the pseudo wire label message, the pseudo wirelabel reflector transfers the pseudo wire label message to a nextreflector according to a switch and transfer mode of its own. The switchand transfer mode of the pseudo wire label reflector includes bothsimple switch and transfer and “next hop self” transfer. Differenttransfer mode adopts different operations which will be describedaccording to the preferred embodiments hereinafter. In step 315, thenext reflector chooses the tunnel between itself and the next hop in thepseudo wire label message as the packet switching network (PSN) tunnelassociated with the pseudo wire label in the pseudo wire label message.In the present specification, “next hop” refers to the label switchingrouter processing the pseudo wire label next on the pseudo wire datalayer, which can be a pseudo wire label reflector or an edge equipmentPE. If the identifier of the next hop is not existed in the pseudo wirelabel message, the source PE is tolerated as the next hop. Then repeatthe steps 310 and 315 until reaching the target PE (step 320).

By the above steps, the pseudo wire label message is transferred to thetarget PE from the source PE via the pseudo wire label reflector. Ofcourse, more than one pseudo wire label reflectors maybe passed through.

In step 325, upon receiving a L2 data package, the target PE determinesthe pseudo wire label of the packed L2 data package and the next hop ofthe PSN tunnel from the received pseudo wire label message. It will bedescribed in detail hereinafter how to determine the pseudo wire labeland the next hop. In step 330, the target PE packs according to thedetermined pseudo wire label and sends the resulted MPLS data package tothe pseudo wire label reflector of the corresponding next hop. In step335, upon receiving the MPLS data package, the reflector determines thepseudo wire label of the packed L2 data package and the next hop of thePSN tunnel from all the received pseudo wire label message of the pseudowire corresponding to the pseudo wire label if the reflector finds thatthe MPLS data package is packed by adopting the pseudo wire labeldistributed by himself according to the pseudo wire label of the MPLSdata package. In step 340, the reflector replaces the primary pseudowire label with the newly determined pseudo wire label and then sendsthe MPLS data package to the next reflector of the corresponding nexthop. Repeat steps 335 and 340 until the next reflector is a source PE(step 350).

Therefore, the L2 PDU could be transported to the source PE (downstreamPE) from the target PE (upstream PE) via the pseudo wire labelreflector. Of course, multiple pseudo wire label reflectors being passedcan be adopted, whose number is the same as that of the pseudo wirelabel reflectors passed for transporting the pseudo wire label message.

It should be noted that upon all the pseudo wire label messages receivedbecome ineffective, the pseudo wire label reflector need to send a labelcancellation message to cancel the pseudo wire label message beingtransferred.

It can be known that from the above description, by adopting the presentembodiment, providing pseudo wire service in the L2 virtual network bythe pseudo wire label reflector could be accomplished.

In the present embodiment, in order to accomplish transferring thepseudo wire label message by the pseudo wire label reflector, the pseudowire label reflector must be enabled to identify the target PE in thepseudo wire label message. However, the existing LDP protocol considersthat the LDP session connection should be established between the sourcePE and the target PE directly and transports the pseudo wire labelmessage on the session connection to establish the pseudo wire.Therefore, the information of the source PE and the target PE are notincluded in the generalized ID FEC element (GID FEC Element) and thevirtual circuit ID FEC element (VCID FEC Element). Therefore, the GIDFEC Element is not adequate to describe a pseudo wire independently.

Therefore, in the invention, the definition of the LDP protocol to theGID FEC Element and the VCID FEC Element as well as the packing formatare extended so that they can carry the information relating to thedouble end PEs of the pseudo wire. In the extended GID FEC Element andthe VCID FEC Element packing format, a SPE-LSR-ID TLV field and aTPE-LSR-ID TLV field are added, which carry label switching router (LSR)identifiers of the source PE and the target PE of the signaling of thelabel switching path (LSP). The definitions of other fields are exactlythe same as the existing LDP signaling protocol.

A bidirectional pseudo wire actually is composed of two unidirectionalLSP. Each LSP of the pseudo wires could be marked: <Source PE, <AGI,SAII>, Target PE, <AGI, TAII>> or <Source PE, <Group, VCID>, Target PE,<Group, VCID>>.

Additionally, the pseudo wire label message could include the identifierof the next hop for informing the LDP peer (PE or reflector) forreceiving the pseudo wire label message about that the pseudo wire labelis distributed or redistributed by the designated next hop. When the LDPpeer which receives pseudo wire label message packs the L2 data packageby adopting the pseudo wire label package and will transfer the L2 datapackage on the pseudo wire, the LDP peer should establish a PSN tunnelwith the next hop designated in the pseudo wire label message. If noidentifier of the next hop is existed in the pseudo wire label message,the source PE is tolerated as the next hop.

In order to cope with the situation of multiple pseudo wire labelreflectors, the priority information of the next hop can also beincluded in the pseudo wire label message. When PE or the reflectorreceives multiple pseudo wire label messages of one pseudo wire, PE orthe reflector could firstly choose the label in the pseudo wire labelmessage whose next priority is the biggest as the label according to thepriority of the next hop; it can also adopt the load balance strategy tochoose the label in a certain pseudo wire label message as the label. Ifno the identifier of the next hop is existed in the pseudo wire labelmessage, there is no priority information of the next hop.

The priority of the next hop could be ranged from 0 to 255. If the nexthop is a source PE, its priority is the highest, 255; otherwise, thepriority of the next hop is ranged from 0 to 254.

If the identifier of the next hop is included in the pseudo wire labelmessage (the priority information of the next hop is not included), itspriority is the lowest, 0.

The information of the source PE and the target PE could be obtained andthe priority of the pseudo wire label message could be supported byadopting the extended LDP protocol and adding the related information ofthe next hop in the pseudo wire label message.

At the beginning of providing the pseudo wire service, both the pseudowire label reflector and the PE need to determine the supportingcapacity of the neighbors to pseudo wire label reflection and identifythe reflector neighbors. Therefore, the invention provides the extendingcapacity negotiation mechanism of the LDP protocol.

Both the PE and the reflector should not send the pseudo wire labelmessage with the extended GID FEC Element, the identifier of the nexthop and the priority information of the next hop to the PE which doesnot support pseudo wire label reflection. In order to not influence thestability of the LDP session and not influence other operations of theLDP, the present invention provides a LDP extension capacity negotiationmessage. By such LDP extension capacity negotiation message, thesupporting capacity of the pseudo wire label reflection could benegotiated dynamically between LDP peers. When the capacity of the LDPpeer changed, the capacity could be renegotiated without interruptingthe LDP session.

The parameters in the extension capacity negotiation message could bepacked in “type-length-value (TLV)” format, including two capacityparameters which can be negotiated, one is the supporting capacityparameter for pseudo wire label reflection, and the other is a parameterwho locally is a pseudo wire label reflector.

The supporting capacity parameter for pseudo wire label reflectionrepresents that whether the present LSR supports pseudo wire labelreflection, whether the present LSR could send the pseudo wire labelmessage with the extended GID FEC Element, the identifier of the nexthop and the priority of the next hop to the present LSR. The parameterwho locally is a pseudo wire label reflector represents whether thepresent LSR is a pseudo wire label reflector.

When the supporting capacity of the pseudo wire label reflector or thePE at one end of the LDP has changed, the pseudo wire label reflector orthe PE can inform the LDP peer its capacity change by automaticnegotiation. If the extension capacity negotiation message of the peeris not received, it is indicated that the peer has no extensioncapacity. When receiving the extension capacity negotiation message, theLSR which does not support the extension capacity negotiation messagecould discard the message.

In the L2 VPN network, all the LDP speakers should adopt a free labelkeeping mode to keep the pseudo wire label and should adopt downstreamindependent label distribution mode when distributing the pseudo wirelabel. The invention is compatible withdraft-ietf-pwe3-control-protocol-06.txt protocol on these two points.

In the draft-ietf-pwe3-control-protocol-06.txt protocol, the label isonly transferred between PE and PE. Therefore, there is no differencebetween the independent label distribution controlling mode and theordered label distribution controlling mode. However, in the invention,all the LDP speakers participating in distributing the pseudo wire label(including PE and the pseudo wire label reflectors) adopt the orderedlabel distribution controlling mode, that is LSR sending the pseudo wirelabel message to the upstream PE or the pseudo wire label reflector onlywhen LSR receives the pseudo wire label message of the downstream PE andLSR itself is the downstream PE of the pseudo wire.

If the PE does not support pseudo wire label reflection, it could onlydistribute the pseudo wire label message to the PE at the other end ofthe pseudo wire. If the PE supports pseudo wire label reflection, thereflector neighbors could be identified automatically by the negotiationcapacity extension message. The PE supporting pseudo wire labelreflection not only distributes the pseudo wire label message to the PEat the other end of the pseudo wire (if there is direct signalingsession between them) on its own responsibility, but also distributesthe pseudo wire label message to all the reflector neighbors.

The pseudo wire label reflector switches the pseudo wire label messageto other pseudo wire reflectors or the target PE in the pseudo wirelabel message only if it receives the pseudo wire label message from thedownstream PE or the downstream pseudo wire label reflector. If thepseudo wire label reflector itself is the target PE in the pseudo wirelabel message, here the pseudo wire label reflector actually is thetarget PE in the pseudo wire label message without transferring thepseudo wire label message to any neighbors. If the target PE in thepseudo wire label message does not support pseudo wire label reflection,the pseudo wire label reflector does not transfer the pseudo wire labelmessage to the pseudo wire label reflector.

If the pseudo wire label reflector receives the pseudo wire labelmessage from the neighbors who do not support pseudo wire labelreflection, it should be considered as that the target PE in the pseudowire label message is the present reflector.

Upon receiving the pseudo wire label mapping message, the target PE inthe pseudo wire label message from the reflector or the downstream PEcould choose the best label according to the priority informationcarried in the pseudo wire label message or could adopt the load balancestrategy to choose the label. Meanwhile, the tunnel led to the next hopLSR in the pseudo wire label message should be chose as a PSN tunnel.

By above-described extension capacity negotiation message, the pseudowire label reflector and the PE could know whether the neighbors supportpseudo wire label reflection and whether they are pseudo wire labelreflector neighbors.

In the present embodiment, the switch and transfer mode for the pseudowire label reflector transferring the pseudo wire label message could beboth simple switch and transfer and next hop self transfer.

FIG. 4 gives a schematic diagram of providing pseudo wire service by thepseudo wire label reflector which adopts the simple switch and transfermode. In the simple switch and transfer mode, the pseudo wire labelreflector does not modify the label value in the pseudo wire labelmessage, the identifier of the next hop and the priority information ofthe next hop. Upon receiving the pseudo wire label message, the pseudowire label reflector transfers the pseudo wire label message toappropriate neighbors directly, wherein “appropriate neighbors” refersto other pseudo wire label reflectors passing the loop detection and thetarget PE, wherein the loop detection refers to the path detectionand/or the hop count detection defined in the existing LDP protocol.

As shown in FIG. 4, the pseudo wire service is provided between PE1 andPE2. There is no direct signaling session connection between PE1 and PE2when establish the pseudo wire LSP in PE1→PE2 direction, but PE1 and PE2establish the signaling session connection with the pseudo wire labelreflector 10. Firstly, PE2 sends the pseudo wire label message in whichthe information of the source PE and the target PE “Source PE=PE2,Target PE=PE1” is carried to the pseudo wire label reflector 10. Uponreceiving the pseudo wire label message, the pseudo wire label reflectortransfers it directly to PE1 due to adopting simple switch and transfermode. Therefore, upon receiving the pseudo wire label message, PE1 couldassociate the pseudo wire label message with the pseudo wire LSP inPE1→PE2 direction according to the information in the pseudo wire labelmessage. Meanwhile, PE1 obtains the in-label distributed by PE2 for thePW LSP in PE1→PE2 direction, because the label is distributed by PE2,i.e., PE2 is the next hop. Therefore, the PSN tunnel is establishedbetween PE1→PE2.

Of course, there could be multiple pseudo wire label reflectors betweenPE1 and PE2. The processing procedure is the same as that of theabove-described pseudo wire label reflector.

In the above simple switch and transfer mode, the pseudo wire labelreflector only participates in the pseudo wire establishing andmaintaining process of the controlling layer rather than the datatransferring process.

FIG. 5 gives a schematic diagram of providing pseudo wire service by thepseudo wire label reflector which adopts the next hop self transfermode. In next hop self transfer mode, the pseudo wire label reflectorparticipates in the pseudo wire label process and the transfer of the L2data package. The pseudo wire label reflector needs to redistribute itslabel for the pseudo wire to replace the label value in the primarypseudo wire label message, and add or modify the identifier of the nexthop and the priority information of the next hop. The pseudo wire labelreflector requires the next pseudo wire label reflector or PE toestablish PSN tunnel with itself by distributing a new label for thepseudo wire and informing the next pseudo wire label reflector or PEwith the identifier of the next hop about that the label in the pseudowire label message is distributed by the pseudo wire label reflector.And the pseudo wire label reflector adopts the new label to pack the L2data package and then transfers to the pseudo wire label reflector viathe PSN tunnel.

As shown in FIG. 5, the pseudo wire label reflector 10 receives thepseudo wire label message sent by PE2, wherein the pseudo wire labelvalue is L1. Then the pseudo wire label reflector 10 distributes thecorresponding in-label L2 and bonds it with the label in the pseudo wirelabel message sent by PE2, then writes it into a in-label transfer listLIB; meanwhile, establishes a PSN tunnel 2 with PE2. The pseudo wirelabel reflector replaces the label value (L1) in the pseudo wire labelmessage with the label value (L2) distributed by itself and add ormodify the identifier of the next hop whose value is the identifier IDof itself. Then, the pseudo wire label reflector 10 sends the modifiedpseudo wire label message to PE1. PE1 establishes the PSN tunnel 1 withthe pseudo wire label reflector 10. Upon packing the data package byadopting the label L2, PE1 sends it to the pseudo wire label reflector10 via the PSN tunnel 1. Then, the pseudo wire label reflector 10replaces label L2 with Ll distributed by PE2 and transfers it to PE2 viathe PSN tunnel 2.

For the L2 VPN in which the pseudo wire label reflector adopts the nexthop self transfer mode, the pseudo wire is still configured between PEs.The pseudo wire label reflector is transparent to the manager of PE.There is no need to make the configuration of the specific pseudo wireLSP, which can be obtained by studying.

FIG. 6 is a schematic diagram of providing pseudo wire service in a L2virtual private network including multiple pseudo wire label reflectors.In present embodiment, there are two pseudo wire label reflectors 10Aand 10B between PE1 and PE2. In this case, PE1 could receive multiplepseudo wire label messages of one pseudo wire. If both the pseudo wirelabel reflector 10A and 10B adopt the next hop self transfer mode, thenext hop in the pseudo wire label message received by PE1 could bedifferent. The priority of the pseudo wire label reflector which adoptsthe next hop self transfer mode could be designated and took in thepseudo wire label message. Therefore, PE1 could choose the pseudo wirelabel reflector whose priority is high as the next hop and choose thecorresponding pseudo wire label as the label according to the priorityinformation of the next hop in the pseudo wire label message. If thepriorities of the next hop are same, the reflector whose identifier issmaller is chose as the next hop. Of course, a certain load balancestrategy could be adopted to share the load on multiple paths.

Two embodiments which use the present invention to accomplishcross-domain pseudo wire service are given below. Generally, LDP is alabel distribution protocol in the domain. When need to providecross-domain pseudo wire service, establishing large numbers ofcross-domain LDP signaling sessions is not appropriate. The managers ofthe autonomous systems could determine to establish a limited number ofLDP sessions between the autonomous systems by negotiation, therebyaccomplish the establishment and maintenance of the cross-domain pseudowire. It could be accomplished by the pseudo wire label reflector.

As shown in FIG. 7, PE1 and PE2 are located at autonomous system 1 andautonomous system 2. When providing pseudo wire service between PE1→PE2,the autonomous domain border router (ASBR) is used as the pseudo wirelabel reflector, that is add the pseudo wire label reflector shown inFIG. 1 on the basis of the primary ASBR or both coincide at the networkand work in the next hop self transfer mode. In this mode, it used asthe next hop of the label switching path LSP.

The pseudo wire label message is sent from PE2 to ASBR2. ASBR2distributes a new label. ASBR2 replaces the primary label in the pseudowire label message with the new label and modify the next hop of thepseudo wire label message into itself (ASBR2). ASBR2 establishes a PSNtunnel 2 with PE2 and then sends the modified pseudo wire label messageto ASBR1. Upon receiving it, ASBR1 distributes a new pseudo wire label.ASBR1 replaces the primary label in the pseudo wire label message withthe new label and modify the next hop of the pseudo wire label messageinto itself (ASBR1). ASBR1 then sends the pseudo wire label message toPE 1. Upon receiving it, PE1 establishes a PSN tunnel 1 with ASBR1.

The L2 data package received from the L2 VPN interface of PE1 is firstlypacked within the pseudo wire label distributed by ASBR1 and sent toASBR1 via PSN tunnel 1. In ASBR1, the pseudo wire label is replaced withthe pseudo wire label distributed by ASBR2 and then the packed datapackage is sent to ASBR2. In ASBR2, the pseudo wire label is replacedagain with the pseudo wire label distributed by PE2 and then the packeddata package is sent to PE2 via PSN tunnel 2 and finally transferred tothe L2 VPN interface of PE2.

In the embodiment, there is no need to establish the PSN tunnel betweenASBR1 and ASBR2 and adopt the pseudo wire label to cross ASBR.

FIG. 8 provides another embodiment providing cross-domain pseudo wireservice, wherein PE1 and PE1 are located at autonomous system 1 andautonomous system 2 respectively. The autonomous domain border routerASBR1 and ASBR2 are not used as the pseudo wire label reflector, but apseudo wire label reflector is added between two autonomous systemsrespectively. Each pseudo wire label reflector works in the next hopself transfer mode. The process providing cross-domain pseudo wireservice is illuminated by taking the PE1→PE2 direction for example.

The pseudo wire label message is sent from PE2 to the pseudo wire labelreflector 2. The pseudo wire label reflector 2 distributes a new label,replaces the primary label in the pseudo wire label message with the newlabel and modifies the next hop in the pseudo wire label message intoitself (the pseudo wire label reflector 2). The pseudo wire labelreflector 2 establishes a PSN tunnel 3 with PE2 and then sends themodified pseudo wire label message to the pseudo wire label reflector 1.Upon receiving it, the pseudo wire label reflector 1 redistributes a newpseudo wire label, replaces the primary label in the pseudo wire labelmessage with the new label and modifies the next hop in the pseudo wirelabel message into itself (the pseudo wire label reflector 1).Meanwhile, the pseudo wire label reflector 1 establishes a PSN tunnel 2with the pseudo wire label reflector 2 and then sends the pseudo wirelabel message to PE 1. Upon receiving it, PE1 establishes a PSN tunnel 1with the pseudo wire label reflector 1.

The L2 data package received from the L2 VPN interface of PE1 is firstlypacked within the pseudo wire label distributed by the pseudo wire labelreflector 1 and sent to the pseudo wire label reflector 1 via the PSNtunnel 1 between PE1 and the pseudo wire label reflector 1. Then thepseudo wire label reflector 1 replaces the pseudo wire label with thepseudo wire label distributed by the pseudo wire label reflector 2 andsent to the pseudo wire label reflector 2 via the PSN tunnel 2 betweenthe pseudo wire label reflector 1 and the pseudo wire label reflector 2.Then the pseudo wire label reflector 2 replaces the pseudo wire labelagain and then sends it to PE2 via the PSN tunnel 3 between the pseudowire label reflector 2 and PE 2 and finally transfer it to the L2 VPNinterface of PE2.

In the embodiment, a PSN tunnel from the pseudo wire label reflector 1to the pseudo wire label reflector 2 is needed between ASBR1 and ASBR2,and the PSN tunnel label is adopted to cross ASBR. This cross-domain PSNtunnel could be established by LDP signaling and also could beestablished by adopting RSVP-TE (resource obligating protocol fluxengineering extension) signaling.

Of course, in both embodiments of FIG. 7 and FIG. 8, the pseudo wirelabel reflectors could adopt simple switch and transfer mode. Here, morecross-domain PSN tunnels are needed to be established which is moreappropriate in the situation of emphasizing the service quality of thepseudo wire.

What is claimed is:
 1. A pseudo wire label reflector comprising: asignaling receiving/sending unit for receiving and sending a labeldistribution protocol signaling message; a pseudo wire label list fordepositing pseudo wire labels and the related information; apacking/unpacking unit for packing a L2 data package into amultiprotocol label switching data package and unpacking a multiprotocollabel switching data package into a L2 data package; a multiprotocollabel switching and transferring unit for receiving and sending amultiprotocol label switching data package; a mode management unit fordetermining the mode for switching and transferring the pseudo wirelabel message; a first session management unit for storing the supportinformation that label distribution protocol signaling sessionconnection supports pseudo wire label reflecting capacity; a firstpseudo wire label receiving unit for receiving the pseudo wire labelmessage; a first pseudo wire management unit for storing the switchedpseudo wire state and determining whether to modify the pseudo wirelabel message according to the switch and transfer mode determined bythe mode management unit; and a first pseudo wire label sending unit forsending the pseudo wire label message.
 2. The pseudo wire labelreflector as claimed in claim 1, wherein the pseudo wire label reflectorfurther comprises a first capacity negotiation unit for exchanging theinformation supporting pseudo wire label reflect capacity withneighbors.
 3. The pseudo wire label reflector as claimed in claim 2,wherein the pseudo wire label reflector further comprises a secondpseudo wire management unit for storing the pseudo wire state when thepseudo wire label reflector is used as an edge equipment.
 4. The pseudowire label reflector as claimed in claim 3, wherein the first and secondpseudo wire management units further comprise: a device for comparingthe priorities of the pseudo wire label messages, a device for choosinga pseudo wire label, and a device for writing the pseudo wire label intothe pseudo wire label list.
 5. The pseudo wire label reflector asclaimed in claim 4, wherein the device for choosing the pseudo wirelabel chooses the pseudo wire label whose priority is the highest as thepseudo wire label.
 6. The pseudo wire label reflector as claimed inclaim 4, wherein the device for choosing the pseudo wire label adopts aload balance strategy to choose the pseudo wire label.
 7. The pseudowire label reflector as claimed in claim 3, wherein the pseudo wirelabel reflector further comprises: a neighbor capacity configurationunit for designating that the neighbors have capacity negotiationfunction.
 8. The pseudo wire label reflector as claimed in claim 1,wherein the pseudo wire label reflector further comprises a secondpseudo wire management unit for storing the pseudo wire state when thepseudo wire label reflector is used as an edge equipment.
 9. The pseudowire label reflector as claimed in claim 8, wherein the first and secondpseudo wire management units further comprise: a device for comparingthe priorities of the pseudo wire label messages, a device for choosinga pseudo wire label, and a device for writing the pseudo wire label intothe pseudo wire label list.
 10. The pseudo wire label reflector asclaimed in claim 9, wherein the device for choosing the pseudo wirelabel chooses the pseudo wire label whose priority is the highest as thepseudo wire label.
 11. The pseudo wire label reflector as claimed inclaim 9, wherein the device for choosing the pseudo wire label adopts aload balance strategy to choose the pseudo wire label.
 12. The pseudowire label reflector as claimed in claim 8, wherein the pseudo wirelabel reflector further comprises: a neighbor capacity configurationunit for designating that the neighbors have capacity negotiationfunction.
 13. A L2 virtual private network, wherein the networkcomprises at least one pseudo wire label reflector claimed in claim 1and at least two edge equipments, wherein each of the at least two edgeequipments comprising: a signaling receiving/sending unit for receivingand sending a label distribution protocol signaling message; a pseudowire label list for depositing pseudo wire labels and the relatedinformation; a packing/unpacking unit for packing a L2 data package intoa multiprotocol label switching data package and unpacking amultiprotocol label switching data package into a L2 data package; amultiprotocol label switching and transferring unit for receiving andsending a multiprotocol label switching data package; wherein each ofthe at least two edge equipments further comprises: a second sessionmanagement unit for storing the information that the neighbors who arepseudo wire label reflectors; a second pseudo wire label receiving unitfor receiving the pseudo wire label message; a third pseudo wiremanagement unit for storing the pseudo wire state; a second pseudo wirelabel sending unit for sending the pseudo wire label message.
 14. The L2virtual private network as claimed in claim 13, wherein the edgeequipment further comprises: a second capacity negotiation unit forexchanging the information supporting pseudo wire label reflect capacitywith neighbors.
 15. The L2 virtual private network as claimed in claim14, wherein the third pseudo wire management unit further comprises: adevice for comparing the priorities of the pseudo wire label messages, adevice for choosing a pseudo wire label, and a device for writing thepseudo wire label into the pseudo wire label list.
 16. The L2 virtualprivate network as claimed in claim 15, wherein the device for choosingthe pseudo wire label chooses the pseudo wire label whose priority isthe highest as the pseudo wire label.
 17. The L2 virtual private networkas claimed in claim 15, wherein the device for choosing the pseudo wirelabel adopts a load balance strategy to choose the pseudo wire label.18. The L2 virtual private network as claimed in claim 13, wherein thethird pseudo wire management unit further comprises: a device forcomparing the priorities of the pseudo wire label messages, a device forchoosing a pseudo wire label, and a device for writing the pseudo wirelabel into the pseudo wire label list.
 19. The L2 virtual privatenetwork as claimed in claim 18, wherein the device for choosing thepseudo wire label chooses the pseudo wire label whose priority is thehighest as the pseudo wire label.
 20. The L2 virtual private network asclaimed in claim 18, wherein the device for choosing the pseudo wirelabel adopts a load balance strategy to choose the pseudo wire label.